Abstract

Measurements (1994–2007) from four cabled-to-shore hydrophone systems located off the North American west coast permit extensive comparisons between “contemporary” low frequency ship traffic noise (25–50 Hz) collected in the past decade to measurements made over 1963–1965 with the same in-water equipment at the same sites. An increase of roughly 10 dB over the band 25–40 Hz at one site has already been reported [Andrew et al., Acoust. Res. Lett. Online 3(2), 65–70 (2002)]. Newly corrected data from the remaining three systems generally corroborate this increase. Simple linear trend lines of the contemporary traffic noise (duration 6 to 12+ years) show that recent levels are slightly increasing, holding steady, or decreasing. These results confirm the prediction by Ross that the rate of increase in traffic noise would be far less at the end of the 20th century compared to that observed in the 1950s and 1960s.

Received 17 December 2009Revised 21 October 2010Accepted 28 October 2010Published online 24 February 2011

Acknowledgments:

No undertaking spanning decades can succeed without the diligent efforts of an entire cadre of people, many of whom have moved on to other careers. The authors will nevertheless attempt to thank the many key personnel who helped along the way: Dr. Kurt Metzger, who served as the original design engineer; Mr. Jack Peeples for engineering expertise, liaison, and coordination in the maintenance of the remote facilities; Mr. Chris Miller, Naval Postgraduate School, Monterey, for liaison and coordination regarding the Pt. Sur facility; Mr. Kurt Dulka, Mr. Al White, Mr. Bob “Fuzzy” Irvin, and Mr. Rodger Pedersen for support at San Nicolas island; Mr. Don Reddaway for construction, testing, installation, and repair of all APL/UW equipment; Mr. Shaun Leach and Mr. Keith Curtis for processing the data for the first decade; Ms. Shirley Weslander for operating and maintaining the systems for the first decade; Ms. Charlotte Leigh (CDR U.S. Navy Ret.) and Drs. Kate Stafford, Mark McDonald and Orest Diachok for science discussions; Ms. Linda Buck for a decade of system operation and data archiving; and Mr. Joe Wigton for system administration both locally and at the remote sites.

This work was originally supported by the ATOC program sponsored by the Strategic Environmental Research and Development Program through the Defense Advanced Research Projects Agency under Grant No. MDA972-93-1-003 and later by the North Pacific Acoustic Laboratory project and the Long Range/Deep Water Propagation initiatives of the Ocean Acoustics Program at the Office of Naval Research under Grants Nos. N00014-97-1-0259 and N00014-1403-1-0181.